In many cameras of the type in which the film is stored in cassette containers, typically in 35 mm cameras, the filmstrip is wound onto a flanged spool that is rotatably supported within a hollow cylindrical shell or housing. A free end portion of the filmstrip, several inches long, which is commonly referred to as the "film leader", protrudes from a light-trapped, plush-lined slit or "mouth" formed between a pair of throat portions of the cassette shell. Commonly, in the process of loading the camera, the back is removed therefrom and the film cassette is inserted into a recess designed to receive it located on one side of the camera. The leader is then manually grasped and pulled from the cassette for a sufficient distance to allow it to be engaged by the camera's film transport mechanism.
While the system described is capable of functioning satisfactorily, it causes considerable mental stress for many individuals, particularly novice photographers, and in fact surveys have shown that the process of loading film cassettes into cameras is regarded by many photographers with considerable trepidation. Some individuals, for example, are concerned about pulling the film leader so far from the mouth of the cassette that the first film frame of the roll will be inadvertently exposed to light during the loading process. Still others worry that the leader will not be properly connected to the transport mechanism, and thus will fail to advance properly within the camera after the latter's closure. In any event, apprehension of the type described tends to discourage individuals from becoming involved in photography, and is therefore, undesirable from a number of standpoints.
The concerns described in the preceding have long been recognized, and a number of approaches have been suggested in efforts to overcome them. In this regard, systems involving special means associated with the film strip to pull it across the film gate of the camera to the winding mechanism have been examined. However, such system often involve special complexities in the film gate, as well as in the windup mechanism, and to that extent, therefore, they are objectionable.
Other methods have been considered which thrust the film out of the cassette and push it through the film gate into the camera's windup device. Notwithstanding resort to such methods, to varying degrees they typically suffer from the fact that the procedures result in damage to the edges of the film and/or cause pressure marks within the film's image area.
Still other processes depend upon inclusion of a stressable member within the cassette, for example a spring, capable of storing energy and releasing it upon the opening of the cassette. The spring causes the film to be extended from its initial position within the cassette to a point at which it is accessible, for example, to a roller drive or sprocket transport system that causes the film to be pulled across the film gate into the camera windup mechanism. Unfortunately, such systems cause the spring to "work" against the plastic film and stress it as a consequence. In addition, these systems require metal springs; consequently, the fabrication of the cassette entirely from plastic is not possible in such instances.